The invention pertains to multi-unit monitoring systems. More particularly, the invention pertains to such units which are capable of wirelessly transmitting status information or parameter values to displaced observers.
Monitoring systems having a large number of interconnected detectors are known to be useful in monitoring various conditions in a region. Various maintenance and test procedures have been developed to facilitate servicing such systems. One testing vehicle has been disclosed in Bellavia et al. U.S. Pat. No. 4,827,244.
Bellavia et al. teach the wireless initiation of a test function. The transmission of information from a detector in both human perceptible and machine readable form is also known.
It would be desirable to facilitate the wireless transfer of information to service personnel in the area of the respective detector. It would also be desirable to be able to implement such transmissions using, if possible, components already present on or in the respective detectors.
An ambient condition detector incorporates a source of radiant energy, for example, an infrared emitting diode, to carry out a sensing function. The source is located within the detector and is not visible from locations outside of the detector.
A control circuit within the detector drives the source with a modulated electrical signal. In a disclosed embodiment, one portion of the signal is associated with a sensing function. Another portion is associated with an external information transfer function. In other embodiments, the sensing related portion could also be modulated with the information to be transferred.
The detector includes an opaque, radiant energy transmissive housing which contains the source. Radiant energy which is emitted from the source passes, in part, through the housing and is radiated from the housing into the surrounding ambient atmosphere. The radiated signal can be sensed and demodulated to extract the transmitted information.
A variety of transmission protocols can be used. Parameter values or status indicators can be transmitted from the detector using analog modulation. Pulse amplitude, pulse position, pulse width or frequency modulation can be used. Other analog modulation processes could be used including phase modulation. Alternately, a binary representation can be transmitted.
In another embodiment, information could be transmitted, using one or more analog protocols, from a light emitting diode. This diode could be located at an exterior peripheral surface of the detector.
In this embodiment, parameter values and status information can be wirelessly transmitted using the modulated waveform. Periods of transmitted signals can be in a range on the order of 3-10 seconds.
In yet another aspect, a portable unit can receive and demodulate the modulated signals. Parameter values or status indicators can be displayed at the unit.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.